#include <stdio.h>

int main(void)
{
    char c = getchar();
    switch (c) {
        case 'a':
            printf("this is a.\n");
            // 注释掉下面这句会打印this is b.为什么呢，查看汇编
            break;
        case 'b':
            printf("this is b.\n");
            break;
        default:
            printf("i don't know what the char is\n");
    }
    return 0;
}